Why do Stars Twinkle?

Twinkle, Twinkle, Little Star

Everybody has heard of the old rhyme that goes, “Twinkle, Twinkle, little star…” Ever wondered why that happens, though? Why do stars twinkle in the first place? What happens to cause the night sky to be full of twinkling sparks of light?

Stars are far, far, away from the earth. Hence, they appear as little bright spots of light to us, even though they are gigantic balls of fire.
The earth has a protective envelope called the atmosphere, which keeps us safe from the harmful radiations of the sun. This atmosphere is made up of various layers, which vary in density.

Stars closer to the horizon Twinkle more!

Light from the stars is visible to us through these layers of atmosphere, which experience varying levels of turbulence (movement of air). As the atmosphere churns, the light from the star is refracted in different directions. This means that some of the light reaches us directly and some gets bent slightly away. This causes us to see varying images of the stars brightness and position, which makes them appear to be twinkling. You might notice that stars closer to the horizon twinkle more. You will notice that stars closer to the horizon will appear to twinkle more than other stars. This is because there is a lot more atmosphere between you and a star near the horizon than between you and a star higher in the sky.

Astronomical Scintillation

So you see, twinkling of the stars is merely an optical illusion! There’s a scientific term for this phenomenon. It’s called “astronomical scintillation”. Sounds heavy doesn’t it? “Twinkling” sounds so much more fun and friendly!

Telescopes like the Hubble telescope are in space, where there is no atmospheric barrier between the stars. Which is why images from these telescopes do not show the stars twinkling.

Do Planets Twinkle in the Night Sky?

Are you wondering why it is the, that planets do not twinkle? The answer is pretty simple. Planets, though far away, aren’t nearly as far away as stars are. Hence, we see a relatively stable image of them. This is actually a good way for us to tell whether the light we see in the sky is a planet or a star.

In the end, this just gives us one more reason to be grateful for the earth’s atmosphere. Not only is it super useful, it also makes watching the night sky a beautiful experience!